We have set out to find, in extreme drought, which species of chaparral are dominant and why they are dominating. We thought that the indicator species of chaparral, Adenostoma fasciculatum, would have highest relative density, relative frequency, and dominance in our research area. Additionally, plants with higher water potential values would have lower percentages of mortality. Chaparral with stronger ability to fluoresce (higher Fv/Fm value) would have lower mortality percentages due to their ability to dissipate excess energy, and therefore reduce water loss. By analyzing our vegetation area using point-quarter sampling system, we were able to record data that show the chaparral shrub with the highest relative density was A. fasciculatum. The chaparral shrub with the highest relative dominance was Adenostoma sparsifolium. The chaparral shrub with the highest relative frequency was Ceanothus cuneatus. Midday water potential values were taken using the Scholander-Hammel Pressure Chamber from the sample site and plotted against the other plants. Arctostaphylos glauca had the lowest water potential (-13.6 MPa) while Malosma laurina had the highest water potential (-3.7MPa). Except for the outlier, Ceanothus spinosus, midday water potentials corresponded negatively to mortality. Fluorescence values and water potential values were positively correlated (R2= 0.7466). Water potential values are positively correlated with chaparral shrub mortality (R2=0.566). Fluorescence also links with chaparral shrub mortality (R2= 0.845).
Doak, Keb; Hubbard, Allison; and Jamison, Alawna, "Community Structure and Differential Mortality of Chaparral during Extreme Drought" (2014). Pepperdine University, Featured Research. Paper 114.